When setting up an extracorporeal blood circuit, as well as when preparing dialyzing fluids for dialysis, a plurality of devices for separating out air are known, such as bubble traps or air-venting devices, whose task is to effectively separate out the gases, which are present and partly dissolved in the fluid from the fluid.
The dialyzing fluids used in dialysis release gases in response to low pressure air separators which usually include a laterally disposed upper inlet, whose intended use is to impress a helical path upon the inflowing fluid. In this context, the air bubbles are to be separated out through a hydrophobic filter situated at the top. An arrangement of this kind is disclosed, for example, by the German Patent No. 32 15 003. However, in practical use, it was determined that the suction created partly entrains the separated air into the outflow so that further precautions had to be taken to improve the separation. Thus, for example, separation aids in the form of small plates were introduced into the venting space. Furthermore, the air separators were often built with very long dimensions to form the largest possible separation surface.
A device is disclosed in U.S. Pat. No. 4,061,031 that can be used both as a flow meter as well as an air separator. The known device has a container, which is divided by a partition wall that includes two chambers, one chamber being provided with an inlet orifice, and the other chamber with an outlet orifice. The partition wall includes an opening, and extends from the bottom of the container up to near the container cover, forming a gap-shaped interstitial space between the inlet chamber and the outlet chamber as well as the container cover.
The cut-through partition wall is comprised of two plate-shaped elements in a staggered arrangement, the orifices of the inlet and outlet chambers being situated at the bottom of the container. Since the opening in the partition wall has a smaller cross-section than the inlet orifice, fluid columns of different heights form in the chambers, making it possible to measure the flow rate. In this context, the difference between the two fluid columns is a measure of the level of the flow rate.
In the known device, the two chambers function as bubble traps. The air bubbles entrapped in the fluid rise to the top of the chambers and remain as gas above the fluid level. An active separation is no longer possible when working with the known device. To keep the fluid from flowing over the top edge of the partition wall into the outlet chamber, the inlet chamber has an elongated shape, which leads to a relatively substantial overall height.